1. Field of the Invention
The present invention relates to a supporting structure of a shaft, and a reduction gear to which the supporting structure of a shaft is applied.
Priority is claimed on Japanese Patent Application No. 2008-251745, filed Sep. 29, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
A reduction gear which has a two-stage speed reduction mechanism in a casing is disclosed in Japanese Unexamined Patent Application Publication No. 2001-323968. In this disclosed example, an inscribed meshing planetary gear speed reduction mechanism is used for the first stage of the speed reduction mechanism, and a bevel speed reduction mechanism is used for the subsequent stage. In the bevel pinion and the bevel gear which constitute the bevel speed reduction mechanism at the subsequent stage, the bevel gear functions as an output gear. An output shaft which supports the output gear is supported by a casing via a bearing. A hollow shaft which has a hollow portion is used as the output shaft.
The reduction gear which has a hollow shaft type output shaft is attached to a partner machine by directly fitting the output shaft into the driving shaft of the partner machine.
In the case of the speed reducer which has the hollow shaft type output shaft as described above, a request for changing the diameter of a hollow portion according to the external diameter of a driving shaft of the partner machine to which the speed reducer is to be attached may occur.
Further, for example, when a structure in which an output shaft is connected with a partner machine by using a joint is adopted, a request for changing the output shaft into a solid output shaft with a key groove may occur. In such a case, since it is not necessary at all to change any portions other than the output shaft of the speed reducer, only the output shaft will be rearranged. However, the supporting structure of the conventional output shaft includes the structure disclosed in Japanese Unexamined Patent Application Publication No. 2001-323968, and the output shaft cannot be rearranged unless portions including a bearing which supports the output shaft are disassembled.